Same here:
Vista, GHC 6.8.3
Tested a bit changed scenario: instead of 20 separate compilations it is
worthwhile to run single, longer build, e.g. ghc --make of same package.
Seems like GHCi does not run garbage collection when machine is busy. And then
it accumulates memory. This renders Vista totally unresponsive and even can lead
to automatic reboot (happened once to me).
:)
--
Gracjan